Susceptor plates can be used to support a substrate during processes, such as epitaxial deposition, etching, thermal oxidation, or the like. In some processes, a susceptor plate may be configured with a central recess, or pocket, and support ledge to support the substrate being processed proximate an outer edge of the substrate. The pocket may serve to assist in the control of substrate temperature by reflecting energy radiated from a backside of the substrate back towards the substrate. The pocket may also serve as a support surface for lift pins while in a retracted position during processing.
One process where such an apparatus is used is a selective epitaxial deposition that utilizes alternating deposition and etch processes. The alternating deposition and etch processes of the selective epitaxial deposition must be carried out at substantially different pressures. For example, the deposition process may be carried out at a pressure of about 10 Torr and the etch process may be carried out at a pressure of about 300 Torr. The pressure differential requires repeated alteration of the chamber pressure, which undesirably slows process throughput. In addition, the inventors have discovered that the pressure must be changed slowly to avoid movement of the substrate on the susceptor plate due to pressure differences between the frontside and backside of the substrate. Unfortunately, the slow change of the pressure between deposition and etch processes further slows process throughput.
The inventors have also discovered that the lift pins can undesirably affect the reflection of radiative energy from the backside of the substrate. As such, the existing configuration of lift pins in the susceptor pocket can result in undesirable non-uniform temperature profiles on the substrate.
Accordingly, the inventors have devised novel susceptor designs, process apparatus, and deposition processes to overcome the above-mentioned limitations.